Isaiah 5:7 (King James Bible) and he looked for judgment but behold oppression for righteousness but behold a cry
The corresponding Hebrew text literally has “and behold” both times. Depending on the context, the original Hebrew and can be translated as but (which is the word the King James translators selected here in Isaiah 5:7). For the Book of Mormon, we do not have the original manuscript for this passage; the printer’s manuscript initially read “and behold” in both cases (with and written as an ampersand), but the second ampersand was crossed out and but supralinearly inserted without any change in the level of ink flow. Thus the Book of Mormon text ends up with the nonparallel “and behold … but behold”. The original Hebrew text and the corresponding King James text argue for parallelism: we should have either two occurrences of “and behold” or two of “but behold”.
So the question is: What is the source of the inserted but in 𝓟? We have no conclusive evidence that Oliver Cowdery (when acting as scribe) referred to a King James Bible in his copying from 𝓞 to 𝓟 (or, for that matter, as he wrote down the original manuscript from Joseph Smith’s dictation). The most probable explanation for the correction in the printer’s manuscript is that the original manuscript read “and behold … but behold”. The first occurrence of “and behold” apparently led Oliver to accidentally repeat this phrase when he copied the text from 𝓞 into 𝓟, but Oliver caught his error and then corrected the second “and behold” to “but behold”.
One wonders, then, if Joseph Smith had perhaps originally dictated “but behold … but behold” (namely, the King James text) but that the scribe in 𝓞 (probably Oliver Cowdery) had accidentally written down “and behold … but behold”. Note that the use of and at the very beginning of this verse (“and he looked for judgment”) could have prompted the scribe to write down “and behold oppression”. Thus it is possible that the original text for 2 Nephi 15:7 read identically to the King James reading. And there is considerable evidence within the manuscripts that the conjunctions and and but were occasionally mixed up. For a list of such mixtures, see the discussion under 1 Nephi 8:20 regarding the use of but in 2 Nephi 9:41.
Ultimately, however, this whole discussion here in 2 Nephi 15:7 involves considerable speculation. The problem is that we have so little evidence to make a firm decision. The most reasonable solution here is to follow the corrected text in 𝓟, under the assumption that it reflects the reading in 𝓞.
Summary: Retain in 2 Nephi 15:7 the corrected reading of the printer’s manuscript (“and behold … but behold”), despite the resulting nonparallelism in an otherwise parallel construction.